In recent years, thin and light weight laptop computers have increasingly been developed. Along with such development, a decrease in thickness as well as enhancement in quality of the protective film of polarizing plates, which are employed in the display apparatuses such as a liquid crystal display apparatus, has increasingly been demanded. Further, liquid crystal image display apparatuses (also called liquid crystal displays) of computers as well as word processors have increasingly been employed in which a reflection minimizing layer is provided to enhance visibility, undesired image capturing is minimized, and in order to achieve display performance of minimizing glare, an anti-glare layer is provided in which the layer surface is roughened.
Various types of anti-reflection layers as well anti-glare layers have been developed depending on their need, and their performance has been improved. In order to enhance visibility, methods are employed in which reflection minimizing function or anti-glare function is achieved by providing various films exhibiting improved performance in front of the liquid display. In an optical film employed as a front plate, provided is a reflection minimizing layer or an anti-glare layer which is formed by coating or sputtering.
The aforesaid anti-glare layer functions as follows. By blurring an image contour reflected on the surface, the visibility of reflected images is degraded. By such action, during the use of an image display apparatus such as a liquid crystal display, an organic EL display, or a plasma display, reflection image capturing becomes almost unnoticeable.
By appropriately roughening the surface, it is possible to provide such properties. Heretofore, disclosed as a method to form such surface roughness has been a method in which minute particles are incorporated into a liquid coating composition (e.g., refer to Patent Document 1). Other than this, known are an embossing method disclosed in JP-A No. 6-234175, and a method disclosed in JP-A No. 63-298201 in which a pattern is previously transferred. However, the embossing method and the method in which roughness is formed by transfer result in low productivity and particularly result in extreme difficulty to form a microscopically roughened structure.
On the other hand, employed as a method to form roughness by using fine particles is a method in which a liquid coating composition is prepared by dispersing minute particles such as minute inorganic or organic particles in binders such as resins and coated, whereby an roughened structure is formed. In this method, minute particles which form roughness are incorporated into a binder layer, wherein it is required to suitably disperse minute particles. As a result, it is difficult to effectively form a desired roughened structure. As a result, problems occur in which it is difficult to result in sufficient anti-glare effects required of the anti-glare film. In addition, when the pattern of roughness is varied, it is necessary to alter the diameter of minute particles, the blending amount, and the layer thickness, whereby conversion of the type of products becomes very complex. Further, in order to form the desired roughened structure, it becomes necessary to use particles of a relatively large diameter, whereby sharpness is degraded. Still further, in the method in which an anti-glare layer is formed employing the aforesaid coating, coating mottle often forms and adhesion to the support or a lower layer is degraded, and further, productivity is also degraded. Accordingly, it has been desired to urgently develop improvement means.
On the other hand, known as one of the methods to form a functional layer is a method in which after applying a liquid coating composition, comprising actinic radiation curable resins or heat curable resins together with various types of minute particles, onto a substrate, curing is performed by irradiation of actinic radiation or thermal processing (e.g., refer to Patents Documents 2-4). However, when an anti-glare layer is formed by coating while employing actinic radiation curable resins or heat curable resins, in order to effectively form the desired roughened structure, in the same manner as above, it is necessary to appropriately control the liquid coating composition as well as coating conditions, whereby the amount of work increases during conversion of product types and productivity is lowered due to the production of numerous types of products.
Still further, in order to improve visibility, heretofore, provided was an anti-glare layer or a reflection minimizing layer on the surface of display apparatuses. Along with the conversion of display apparatuses to color as well as to higher resolution, an anti-glare film is sought which exhibits excellent visibility.
(Patent Document 1)
Japanese Patent Publication Open to Public Inspection (hereafter, it is called as JP-A) No. 59-58036 (claims)
(Patent Document 2)
JP-A No. 2001-310912 (claims)
(Patent Document 3)
JP-A No. 2002-114928 (claims)
(Patent Document 4)
JP-A No. 2002-120311 (claims)